Leetcode:minimum_ depth_ of_ binary_ Tree solutions

Hello everyone , I meet you again , I'm the king of the whole stack

One 、 The title of

And seek the deepest binary similarity . Given binary tree . Find the minimum depth .

The minimum depth is along the root node , The shortest path to the leaf node .

Two 、 analysis

When I see this topic . I directly changed the code of the deepest binary tree slightly , hold max Change to min. I thought there should be no problem , Who knows WA Twice , I calmed down and looked . Finally I know , When a node is NULL It's about to end . The next time, no matter how simple the topic is, you should calm down and analyze it carefully , Otherwise easy error .

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int minDepth(TreeNode *root) {
        if(root==NULL) 
        	return 0;
        int mleft=minDepth(root->left);
        int mright=minDepth(root->right);
        if(mleft==0)
           return 1+mright;
        else if(mright==0)
           return 1+mleft;   
        else return min(mleft,mright)+1;
    }
};

 Two 、

 
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

class Solution {
public:
    int minDepth(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        return minRec(root);
    }
    
    int minRec( TreeNode * root) {
        if(!root) return 0;
        
        int left = minRec( root->left);
        int right = minRec( root->right);
        
        if(left && right) return 1 + min(left, right);
        if(left || right) return 1+left+right;
        return 1;
    }
};
 3、 ... and 、

 
/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int minDepth(TreeNode root) {
        // Start typing your Java solution below
        // DO NOT write main() function

        return minRec(root);
    }
    
    private int minRec(TreeNode root) {
        if(root==null) return 0;
        
        int l = minRec(root.left);
        int r = minRec(root.right);
        
        if(l==0) return r+1;
        if(r==0) return l+1;
        
        return Math.min(l, r) + 1;
        
    }
}

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